Coalescence in an interface-modified polymer blend as studied by light scattering measurements

• Published in: Polymer (Guilford) Vol. 37; no. 3; pp. 509 - 517
• Main Authors: SONDERGAARD, K, LYNGAAE-JORGENSEN, J
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.1996; Elsevier
• Subjects: Applied sciences; blends; coalescence; Exact sciences and technology; interface; Organic polymers; Physicochemistry of polymers; Properties and characterization; Thermal and thermodynamic properties; interface; coalescence; blends; Molten state; Liquid liquid interface; Diblock copolymer; Methyl methacrylate polymer; Styrene polymer; Kinetics; Coalescence; Experimental study; Methyl methacrylate copolymer; Mechanism; Heterogeneous mixture; Styrene copolymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/0032-3861(96)82923-5

The influence of A—B diblock copolymers on coalescence in A:B blends has been studied by rheo-optical measurements and electron microscopy. Divergent criteria and experimental evidence appear in the literature on the block copolymer (BC) molecular weight ( M W) and volume fraction ( ϕ bc) when the requirement is the BC to reside at the interface. In the present study the block chain lengths were chosen shorter than the corresponding homopolymers as a starting point. For selected model systems it was found that symmetrical diblock copolymers with ϕ bc ≥ 1% were most effective for inhibiting coalescence. However, rheo-optical measurements revealed that the stabilization effect is not unconditional during the flow; coalescence is prevented for a time which decreases with increasing shear rate due to removal of the BC away from the interface. The origin of the observed behaviour is discussed based on various mechanisms: shear-induced mutual compatibility between components, squeeze-out/drainage of the interfacial layer, frictional pull-out of BC chains, collision-induced entrapment of BC between interfaces, encapsulation of the BC based on the concept of elastic interfacial curvature.